Kinetic energy inherent in the earth's atmosphere, in the form of wind power, has long been utilized to perform useful work. Power is extracted from horizontal air movements by windmills and the like employing blades or vanes rotatable about a horizontal axis and arranged to intercept the wind to develop sufficient torque to drive small pumps, generate electrical power at limited levels or drive small mills. Past windmills, however, have been inefficient and capable of developing only limited power.
More recently, several large tower mounted units have been built and tested with a somewhat improved efficiency but at a substantial cost when considering the energy produced as compared with other power generating means. Further, these large units require heavy, bulky towers and bracing and require complex drive and feathering means for high wind velocity protection. A complicated yaw mechanism, to bring the rotatable blades into a favorable position relative to the wind direction, is also needed.
Research has also been conducted to develop a wind turbine with three intricate aircraft-type rotor blades formed in a catenary shape for rotation about a vertical axis. Therein, much of the blade's efficiency is lost because both blade ends are mounted for rotation about the axis with little power developed remote from the catenary centers.